Tread for recapping tires



Nov. 8, 1966 w. SCHELKMANN TREAD FOR REGAPPING TIRES Filed Oct. 20, 19

2 ts-Sheet 1 K an-LL11 J. firm,

Nov. 8, 1966 w. SCHELKMANN 3,283,795

TREAD FOR RECAPPING TIRES Filed Oct. 20, 1964 2 Sheets-Sheet 2 Unitedtates Patent 3,283,795 TREAD FOR RECAPPING TERES Wilheirn Schelirniann,tCrengeldanzstrasse 85a, Witten (Ruhr), Germany Fiied Oct. 20, W64, Ser.No. 495,045 21 Claims. (Cl. l52187) The present invention relates to atread for recappmg tires.

It is known to recap tires with pre-vulcanized profiled treads by meansof a layer of binder material sandwiched between the outer surface ofthe tire and the tread, in which the parts to be united by vulcanizationare wrapped in a flexible air-tight cover sheet so that the cover sheetforms a closed wrapper over the parts, and in which air and other gasesare removed from the closed wrapper so that the parts will be pressed byatmospheric pressure substantially without clearance against each other.The thus assembled parts enclosed air-tightly in the wrapper are thensubjected in an autoclave to heat and pressure, whereby the tread ispermanently bonded to the outer tire surface by the layer of bindermaterial.

Such a method is for instance disclosed in the US. Patent 2,966,936 andsuch a method is also disclosed in the copending application Serial No.364,385.

Considerable difficulties are encountered in such a method of recappingtires to positively prevent any air enclosure between the bottom surfaceof the tread and the outer tire surface during application of the treadto the outer tire surface, especially if the bottom surface of the treadis curved in direction transverse to its elongation.

Another difficulty arises from the fact that the outer tire surface,curved in direction transverse to its circumference, has in a plane ofsymmetry of the tire normal to the tire axis a circumference of agreater length than the circumference of the tire at the opposite sideportions thereof. When an elongated tread is wrapped around the outertire surface, the central portion of the tread will extend over aportion of the outer tire surface having a greater circumferentiallength than the side portions of the tread and therefore, the centraltread portion has to be expanded or the. side portions have to becontracted to compensate for the difference in the circumferentiallength of the outer tire surface, which will create in a tread of knownconstruction undue stresses in the tread which will detrimentally affectits wear and/ or the bond between the inner tread surface and the outertire surface to be recapped.

It is an object of the present invention to overcome these difficultiesduring application of a tread to the outer surface of the tire to berecapped and during subsequent bonding of the tread to the tire surface.

It is a further object of the present invention to provide for a treador tread sections to be applied and subsequently to be bonded to a wornouter tire surface, which are constructed in such a manner that airenclosures between the inner tread surface and the outer tire surfaceduring application of the tread or tread sections to the outer tiresurface is positively prevented.

It is an additional object of the present invention to provide for anelongated tread which can be applied to the outer tire surface and whichis constructed in such a manner that the difference between thecircumferential length of the outer tire surface in a plane of symmetryof Fatented New. 8, 1966 the tire normal to the tire axis and thecircumferential length at the side portions of the tire can. be easilycompensated for without creating in the tread undue stresses which woulddetrimentally affect its wearing quality as Well as the bond betweentread and tire.

With these objects in view, the tread section according to the presentinvention for recapping a tire having an outer surface of apredetermined curvature transverse to the circumference of the tire isprovided with an inner surface which is curved in direction transverseto the elongation of the tread section along a radius of curvature whichis greater than that of the tire. Preferably, the inner surface of thetread is also curved in direction of its elongation along a radius ofcurvature which is greater than that of the tire in the aforementioneddirection. When a tread having an inner surface curved as set forthabove is applied against the worn outer tire surface, a central portionof the tread will first engage the outer tire surface so that as theinner tread surface is subsequently applied over its whole area to theouter tire surface any air between the inner tread surface and the outertire surface will be gradually squeezed out between the surfaces so thatair enclosures between these surfaces are positively avoided.

According to the present invention the tread may also be formed with aplurality of expandable and contractable means, for instance folds,extending spaced from each other and transverse to the elongation of thetread so that during application of the tread about the tire thedifference between the length of the circumference of the outer tiresurface in a plane of symmetry of the tire normal to the tire axis andthe length of the circumference at side portions of the outer tiresurface may be compensated for by expanding or contracting the folds inthe tread so that the tread may be properly applied to the outer tiresurface without creating undue stresses in the tread.

The novel features which are considered as characteristie for theinvention are set forth in particular in the appended claims. Theinvention itself, together with additional objects and advantagesthereof, will be best understood from the following description ofspecific embodiments when read in connection with the accompanyingdrawings, in which:

FIG. 1 is a partial cross sectional view of a tire to be recapped and atread section placed against the outer tire surface, the section throughthe tire being taken along a plane including the tire axis;

FIG. 2 is a bottom view of the tread section drawn to a smaller scale;

FIG. 3 is a partial side view of a tire and a plurality of treadsections placed against the outer tire surface;

FIG. 4 is a partial sectional view of a further modification showing apair of tread sections to be applied to a tire;

PEG. 5 is a partial cross sectional view of an additional modificationshowing a plurality of tread sections placed side by side on the outertire surface;

FIG. 6 is a view similar to FIG. 5 and showing a modification of treadsections to be placed side by side on a tire;

FIG. 7 is a cross sectional view of a tread section which may be placedbetween the tread sections of FIG. 6;

FIG. 8 is a cross sectional view similar to FIG. 5 showing a pair oftread sections to be placed side by side on 1:9 the outer tire surfaceand an insert connecting the tread sections;

FIGS. 9 and 10 are cross sectional views similar to FIG. 8 and showingfurther modifications of a pair of tread sections to be placed side byside on a tire;

FIG. 11 is a schematic view showing in cross section part of a tire andthe tread to be applied thereto;

FIG. 12 is a partial cross sectional view showing the application of atread to the outer tire surface by means of a pressure roller in whichthe tread is provided With folds;

FIG. 12a is a partial cross sectional view of another tread which may beapplied with a pressure roller;

FIG. 13 is a partial bottom view of a tread similar to that shown inFIG. 12;

FIG. 14 is a sectional side view similar to that shown in FIG. 12 andshowing a modified tread during its application onto the outer surfaceof a tire;

FIG. 15 is a partial side view of a tread similar to that shown in FIG.14-; and

FIG. 16 is a partial section of a tread similar to that shown in FIG.15.

Referring now to the drawings and more particularly to FIGS. 1-3, itwill be seen that the tire 1 to be recapped has an outer tire surface 1'which is curved in a plane including the tire axis along a radius ofcurvature 3. The tread section 2 to be applied against the outer tiresurface 1' and to be subsequently bonded thereto has a bottom surface 4curved along a radius of curvature which is greater than the radius 3.As shown in FIG. 3 a plurality of sections 2 are placed about thecircumference of the tire so that the end faces 14 of the sections mayabut against each other and be bonded to each other after the sections 2are applied against the outer tire surface. The bottom surface of eachsection 2, as initially formed, is also curved in longitudinal directionalong a radius of curvature 12 which is greater than the radius 11 ofthe tire. When the tread sections 2, as initially formed are placedagainst the outer tire surface, the bottom surface 4 of each treadsection will engage the worn tire surface 1' to be recappedsubstantially along a point 13 which is located midway between the endfaces 14 of each section and midway between the side faces 6 thereof.

When the sections 2 are now pressed against the worn tire surface 1 sothat the bottom face 4 of each section engages over its whole area theworn out tire surface 1', any air between the surfaces 4 and 1' will begradually pressed out from the central portion 13 of the tread at whichthe bottom surface 4 initially engages the worn tire surface 1 towardthe outer edges of the tread so that air enclosures between the surfaces4 and 1' during tight application of the bottom surface 4 of the treadagainst the worn out tire surface 1' are positively avoided.

Preferably, the tread 2 is also formed with a plurality of bores 8therethrough, as best shown in FIGS. 1 and 2 and the bottom ends ofthese bores may also be connected by a network of grooves 9, as shown inFIG 2, to further facilitate escape of air from the space between thesurfaces 4 and 1 during tight application of the bottom surface 4 of thetread against the outer worn surface 1' of the tire.

Each of the treads has preferably side faces 6 inclined at an acuteangle to the bottom surface 4 so as to form on each tread wedge-shapedside portions 7 as best shown in FIG. 1. The outer surface of the tire,as initially produced is preferably curved in direction transverse tothe elongation of the tread along a radius of curvature Which is greaterthan the radius of curvature 5 of the bottom surface 4 of the tread.

The tread sections 2 are preformed and/or prevulcanized with theaforementioned radii of curvature in a mold and subsequently cooled. Thesections are then removed from the mold and heated without beingconfined at low temperature in a pressurized fluid such as vapor, air,water or glycerine. The thus produced mold sections will resilientlycontain the original shape to which they are molded during subsequentstorage of the sections.

Instead of forming the tread sections with a width substantially equalto the widths of the tire to be recapped, it is also possible accordingto the present invention to provide two or three tread sections to beplaced side by side to cover the widths of the tire and suchmodifications are shown in FIGS. 4-10.

According to FIG. 4 the tread is formed by a right part and a left part16, as viewed in FIG. 4, each covering substantially half of the widthof the tire to be recapped and each of the tread parts 15 and 16 has aninner side face 17 of castellated configuration so that parts of eachside face extend normal and parts parallel to the axis 18 of the tire tobe recapped. When the parts 15 and 16 of the tread are applied to thetire the castellated side faces 17 will interengage with each other asshown in FIG. 4.

Instead of forming the tread from two parts, it is also possible to formthe tread out of three parts as shown in FIG. 5, which illustrates apair of side parts 19 and 20 and a central part 21 sandwiched betweenthe side parts. Each of the side parts 19 and 20 has a bottom facecurved along a radius of curvature 22 which is greater than thecorresponding radius of curvature 23 of the outer tire surface so thatthe side parts 19 and 20 will initially engage the outer tire surface ata central portion 24 as indicated in FIG. 5. The bottom face of thecentral portion 21, on the other hand, may be straight in a crosssection extending transverse to the elongation of the central part.

Further tread modifications according to the present invent-ion in whichthe tread is formed out of two or more parts are shown in FIGS. 6-10.FIG. 6 shows an arrangement in which the left part 25 of the tread isformed at an upper inner portion thereof with a cutout 25 to form at thelower inner portion thereof a projection 25", Whereas the right part 26is formed at a lower inner portion thereof with a cutout 26 resulting ina projecting portion 26 at an upper inner portion of part 26. If thetread parts 25 and 26 are to be applied against a tire of relativelysmall Width the projecting portions 25" and 26" will be placed in thecorespond-ing cutouts 25 and 26', or if the tread is. to be used on atire of relatively great width, a third intermediate part 27 as shown inFIG. 7 may be sandwiched between the left and right part 25 and 26 shownin FIG. 6 with the projection 28 of the intermediate part 27 located inthe cutout 25 and the projection 28 located in the cutout 26.

A further modification is shown in FIG. 8 in which the left part 29 andthe right part 29, as viewed in FIG. 8, are each formed with a groove36) of substantially rectanguilar cross section extending from the innerside face of each part thereinto and an insert 31 formed from the sameor similar material as the parts 2% and 29' may be inserted in thegroove formed in the two parts so as to substantially fil'l the grooves.

A further modification is shown in FIG. 9 in which the left part 32, asviewed in FIG. 9, is for-med with a concavely curved inner side face 34,whereas the right part 33 is formed with a convexly curved side face 35projecting into the groove formed by the concavely curved side face 34of the left part 32.

FIG. 10 shows an additional modification in which the left part 36, asviewed in FIG. 10, as Well as the right part 36 are each formed with aconcavely curved inner side face 37 of substantially semi-circularconfiguration and in which an insert of substantially circular crosssection is sandwiched between the left and right part and substantiallyfilling the grooves formed by the concavely curved inner side faces 37.

It is to be understood that the bottom faces of the parts 15, 16, 25 and26, 29 and 29", 32 and 33, and 36 and 36' are initially formed with acurvature as explained above in connection with FIGS. 1 and 5.

The tread parts shown in FIGS. 4-10 may be initially molded andprocessed in the manner as described above either in strip form or incircular form. When manufactored in strip form the strip may be cut to alength substantially equal to the maximum circumference of the tire tobe recapped or the strip may be formed in several sections as indicatedin FIG. 3 which are then preferably curved in longitudinal direction andin the manner as described in connnection with FIG. 3. Likewise, whenthe tread is initially molded in circular form, the parts may be made inform of a plurality of ring segments or as integral annular members.

As mentioned above, it is also an important feature of the presentinvention to provide for a tread by means of which the differencebetween the circumferential length of the outer tire surface at theplane of symmetry of the tire normal to the tire axis and thecircumferential length at the side portions of the tire can becompensated for. This is especially important in treads which aremanufactured in strip form and in which the tread extends over the sideportions of the tire to be recapped as shown in FIG. 1. If stripsmanufactured in strip form are placed on the t-raversely curved outersurface of the tire to be recapped and about the circumference of thetire, there will be created either a tension in the central portion ofthe tread which extends about the maximum circumferential length of thetire or a compress-ion at the side portions of the profile which willset up in the tread when applied about the circumference of the tireundue stresses which will detrimentally affect the wearing quality of tre tread and/ or the bond between tread and tire.

This dilficulty in the application of strip-shaped treads is overcomeaccording to the present invention by providing treads which areconstructed in such a manner that the central longitudinal portion ofthe tread which during wrapping of the tread about the tire aresuperimposed upon the maximum tire circumference are made expandablewhereas the longitudinal edge portions of the tire are constructed insuch a manner so as to maintain their length during wrapping of thetread about the tire, or the treads according to the present inventionare constructed in such a manner that the central longitudinal portionwill maintain its length during wrapping of the tread about the tire,whereas the lateral edge portions of the tread can be contracted.

According to the present invention the difference in length between thecentral portion and the longitudinal side portions of the strip-shapedtread may be compensated for by forming of folds in the tread stripextending spaced from ea h other and transversely to the elongation ofthe strip, which have their greatest Widths at the central portion ofthe tread and which decrease in width toward the opposite edge portionsthereof. The folds are dimensioned in such a manner that during wrappingof the strip about the transversely curved outer tire surface thedifference between the circumferential length of the central portion ofthe tire and the side portions thereof are compensated o that the treadcan be applied to the outer tire surface without creating undue tensionsin the tread.

In a profiled tread which has spaced projections connected by a Web orbase portion, the folds may be arranged in the web portion and mayextend upwardly between the projections or downwardly below the bottomsurface of the web.

Instead of expanding the central portion of the tread strip, it is alsopossible to shorten or compress the opposite edge portions thereof andfor this purpose, the web portion of the profiled tread may be formedwith cutouts extending from the bottom surface of the tread into the webportion transverse to the longitudinal direction of the head and eachtapering from the longitudinal edge portion of the tread toward thecenter region thereof, which cutouts will be at least partly closedduring wrapping of the tread about the tire surface.

It is also possible to provide for the necessary expansion of the centerportion of the tread by forming a plurality of slits extending from thebottom surface of the tread strip through the web portion thereof intothe respective projections which will open at the center portion i ofthe tread during wrapping of the tread about the tire. The thus formedcavities may be filled with binding material and for this purposeappropriate bores may be formed in the projections.

In order to expand or contract the plurality of folds or cutouts inuniform manner during Wrapping of the tread about the tire surface, itis preferred according to the present invention to use a pressure rollermounted turnably about an axis parallel to the tire .axis and providedabout its circumference with radial projections app-ropriately spacedand formed to mesh with the projections on the profiled tread duringwrapping of the tread about the tire surface while the tire and thepressure roller are respectively rotated about their axes.

FIG. 11 schematically illustrates a transverse cross section throughpart of a tire I and a tread 2 applied thereagainst. The radius of thetire in a plane of symmetry normal to the tire axis 18 is R1 which isconsiderably greater than the radius R2 of the tire adjacent to the sideportion thereof. Evidently the circumferential length of a circle in theplane of symmetry passing through the point a is considerably greaterthan the circumferential length of a circle passing through the point b.This difference between the two circumferential lengths has to becompensated for if a strip-shaped tread is wrapped about the outer tiresurface for recapping the same.

P16. 12 shows a tread strip at according to the present invention inwhich a plurality of folds are respectively formed between theprojections 42 of the profiled tread strip. The folds 43 extend upwardlyfrom the web portion 41 and as mentioned above, each of the folds hasits greatest width at the center portion of the strip and tapers towardsthe edge portion thereof. During wrapping of the tread 49 about theouter surface of the tire I the folds are stretched as indicated betweenthe projections 42a and 42b so that the central longitudinal portion ofthe tread is thereby elongated.

FIG. 12a shows a slight modification of the tread strip shown in FIG. 12and the folds 43" of the tread 40 illustrated in FIG. 12a extend in thiscase downwardly below the bottom surface of the tread strip.

If it is desired to maintain the length of the central portion of thestrip while shortening the length of the edge portions thereof duringwrapping of the strip about the tire surface, it is also possibleaccording to the present invention to provide a plurality of spacedcutouts 4-8 extending through the web portion and into the respectiveprofiles and which respectively taper from the respective outer edge ofthe tread towards the center portion thereof as best shown in FIG. 13.During application of the tread 49 onto the outer surface, as shown inFIG. 14 the cutouts 48 will be closed as shown in the projections 4 'aand iZb at the right side of FIG. 14. In this case the length of thecentral portion of the tread strip will be maintained, whereas thelength at opposite edge portions of the tread will be contracted.

It is also possible to form in the central portion of each projection42" of a tread 51 a slit 52 extending upwardly from the bottom surfaceof the tread into the respective projection, as shown in FIG. 15, sothat during application of the tread about the tire surface the slit 52may be expanded as shown at 54 in FIG. 15 so as to compensate for thenecessary greater length at the central portion of the tread duringapplication thereof onto the tire surface. The flanks of the projection42 may be formed with slight undercuts 53 as shown at the leftprojection illustrated in FIG. 15 so that after expansion of the slitthe flanks will be substantially straight as shown at the rightprojection in FIG. 15.

The tread according to the present invention may also be formed withbores 56 communicating with the cavities 48 at one end and with theouter tread surface on the other end (FIG. 16) to assure that duringclosing of the cavities 48, the air originally contained therein mayescape 3 therefrom. The cavities may also be at least partly filled withbinding material to assure that after contraction the tread portionswill be maintained in the contracted position. The bores 56 will alsofacilitate escape of surplus bin-ding material from the contractedcavities. The tread 55 shown in FIG. 16 has a plurality of cutouts 4& ineach projection.

As mentioned above the tread as shown in FIGS. 12-16 is preferablyapplied against the outer surface by means of a pressure roller asillustrated in FIGS. 12 and 14. The pressure roller 44 is provided atits circumference with a plurality of radially extending projections 45which are spaced from each other and which are formed with profilesmeshing with the profile of the tread so as to uniformly expand thefolds 43 as shown in FIG. 12 at the central portion of the strip or touniformly compress thetread strip at the side portions thereof to closethe cutouts 48 as shown in FIG. 14.

During application of the tread strip, the tire and the pressure roller44 are mounted on an appropriate support, not shown in the drawings, sothat the tire may be rotated about its axis 18 whereas the pressureroller is [rotated about its axis 46. During such rotation theprojections 45 of the pressure roller will mesh with the projections 42,42 of the tread strip to provide for uniform expansion or unifonm[contraction of the respective portions of the tread strip. Of course,to apply tread strips with different profiles, that is projections ofdifferent contour and spacing, different pressure rollers will have tobe used in which the projections 45 are spaced and contoured accordingto the projections on the tread. Furthermore, the supporting frame forthe tire and the pressure roller has to 'be constructed in such a mannerthat the distance between the axis 18 of the tire and the axis 46 of thepressure roller :may be changed so that treads can be applied properlyto tires of different diameter.

After the tread has been properly applied to the outer tire surface, theends of the tread are provisionally secured to each other in any wellknown manner, and subsequently the tread is vulcanized to the tire inthe manner as set forth in the above mentioned patent or as set forth inthe copending application. Before applying the tread of the outer tiresurface, the latter may also be covered with a layer of binder material.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types oftreads for recapping tires differing from the types described above.

While the invention has been illustrated and described as embodied in atread for recapping tires having a transversely curved outer surface, itis not intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A tread section for recapping a tire of a given radius, said treadsection having an inner continuously curved concave surface adapted toengage the outer surface of the tire to be recapped, said inner concavesurface being curved in the direction of the circumference of the tireprior to its engagement with the latter along a radius of curvaturegreater than that of said tire.

2. A tread section for recapping a tire having an outer surface of apredetermined curvature transverse to the circumference of the tire,said tread section having an inner continuously curved concave surfaceadapted to engage the outer surface of the tire to be recapped, saidinner concave surface being curved in a direction transverse to thecircumference of the tire along a radius of curvature greater than thatof said tire.

3. A tread section for recapping a tire having an outer surface of apredetermined clurvature transverse to the circumference of the tire,said tread section having an inner continuously curved concave surfaceadapted to engage the outer surface of the tire to be recapped, saidinner concave surface being curved in a direction transverse to thecircumference of the tire along a radius of curvature greater than thatof said tire and said tread section having an outer surface curved insaid direction around a radius of curvature which is greater than thatof said inner surface the center of the radius of curvature of saidouter surface being spaced from that of said inner surface.

4. A tread section for recapping a tire having an outer surface of apredetermined curvature transverse to the circumference of the tire,said tread section having an inner continuously curved concave surfaceadapted to engage the outer surface of the tire to be recapped, saidinner concave surface being curved in a direction transverse to thecircumference of the tire along a radius of curvature greater than thatof said tire, said tread section having a side face including with saidinner surface an acute angle to form in a cross section transverse tothe elongation of said section a side portion of wedge-shapedconfiguration.

5. Tread means for recapping a tire having an outer surface ofpredetermined curvature transverse to the cir cumference of the tire,said tread means including two tread sections adapted to be arranged onthe tire respectively at opposite sides of a plane of symmetry normal tothe tire axis and each of said tread sections having an innercontinuously curved concave surface curved in a direction transverse tothe circumference of the tire along a radius of curvature greater thanthat of the tire.

6. Tread means for recapping a tire having an outer surface ofpredetermined curvature transverse to the circumference of the tire,said tread means including two tread sections adapted to be arranged onthe tire respectively at opposite sides of a plane of symmetry normal tothe tire axis and each of said tread sections having an innercontinuously curved concave surface curved in a direction transverse tothe circumference of the tire along a radius of curvature greater thanthat of the tire, each of said sections having an outer side faceincluding with said inner surface of said section an acute angle to formon each section an outer side portion of wedge-shaped configuration.

'7. Tread means for recapping a tire having an outer surface ofpredetermined curvature transverse to the circumference of the tire,said tread means including two annular tread sections adapted to bearranged on the tire respectively at opposite sides of a plane ofsymmetry normal to the tire axis and each of said tread sections havingan inner continuously curved concave surface curved in a directiontransverse to the circumference of the tire along a radius of curvaturegreater than that of the tire.

8. Tread means for recapping a tire having an outer surface ofpredetermined curvature transverse to the circumference of the tire,said tread means including two annular tread sections adapted to bearranged on the tire respectively at opposite sides of a plane ofsymmetry normal to the tire axis and each of said tread sections havingan inner continuously curved concave surface curved in a directiontransverse to the circumference of the tire along a radius of curvaturegreater than that of the tire,

9 the maximum circumference of said inner surface being slightly greaterthan the maximum circumference of the outer tire surface to be recapped.

9. Tread means for recapping a tire having an outer surface ofpredetermined. curvature transverse to the circumference of the tire,said tread means including two annular tread sections adapted to bearranged on the tire respectively at opposite sides of a plane ofsymmetry normal to the tire axis and each of said tread sections havingan inner continuously curved concave surface curved in a directiontransverse to the circumference of the tire along a radius of curvaturegreater than that of the tire; and a central tread. section arrangedbetween the aforementioned sections, said central tread section havingan inner cylindrical surface having straight generatrices.

10. Tread means for recapping a tire having an outer surface ofpredetermined curvature transverse to the circumference of the tire,said tread means including two tread sections adapted to be arranged onthe tire respectively at opposite sides of a plane of symmetry normal tothe tire axis and each of said. tread sections having an innercontinuously curved concave surface curved in a direction transverse tothe circumference of the tire along a radius of curvature greater thanthat of the tire, each of said tread sections having staggered innerside faces facing and interengaging with that of the other section.

if. Tread means for recapping a tire having an outer surface ofpredetermined curvature transverse to the circumference of the tire,said tread means including two tread sections adapted to be arranged onthe tire respectively at opposite sides of a plane of symmetry normal tothe tire axis and each of said tread sections having an innercontinuously curved concave surface curved in a direction transverse tothe cirrumference of the tire along a radius of curvature greater thanthat of the tire, each of said tread sections having an inner side facefacing that of the other section and each of said sections being formedwith a groove extending from said inner side face thcreinto; and aninsert extending from the groove in one section into that of the othersection and substantially filling said grooves in said sections.

12. Tread means as set forth in claim 11 wherein each of said grooveshas a substantially rectangular crosssection.

13. Tread means as set forth in claim 11 wherein each of said grooveshas a substantially semicircular crosssection.

14. Tread means for recapping a tire having an outer surface ofpredetermined curvature transverse to the circumference of the tire,said tread means including two tread sections .adapted to be arranged onthe tire respectively at opposite sides of a plane of symmetry normal tothe tire axis and each of said tread sections having an innercontinuously curved concave surface curved in a direction transverse tothe circumference of the tire along .a radius of curvature greater thanthat of the tire, each of said tread sections having a side face facingthe side face of the other section, the side face of one section beingin a plane normal to the elongation of said section concavely curved andthe side face of the other section being convexly curved, and said othersection extending with the concavely curved side thereof into the grooveformed by the oonvexly curved side face of said one section.

15. An elongated substantially straight tread for recapping tires havingan outer surface of a predetermined curvature transverse to thecircumference of the tire, said tread having an inner continuouslycurved concave surface adapted to engage the outer surface of the tireto be recapped, said inner surface being curved in direction transverseto the elongation of said tread along a radius of curvature greater thanthat predetermined curvature of said tire, said tread. being formed witha plurality of expandable and contractable folds extending spaced fromeach other and transverse to the elongation of said tread so that duringapplication of said tread about the tire with the inner surface of saidtread abutting against the outer surface of the tire, the differencebetween the length of the circumference of the outer tire surface in aplane of symmetry of the tire normal to the tire axis and the length ofthe circumference at side portions of the outer tire surface may becompensated for by expanding or contracting said folds in said tread.

l6. A tread as set forth in claim 15, wherein said tread is a profiledtread having a web portion and a plurality of projections spaced indirection of the elongation of said tread from each other and projectingupwardly from said web and wherein said folds are formed by portions ofsaid web between said projections and extending downwardly beyond saidinner surface.

17 A tread as set forth in claim 15, wherein said. tread is a profiledtread having a web portion and a plurality of projections spaced indirection of the elongation of said tread from each other and projectingupwardly from said web and wherein said folds are formed by portions ofsaid web between said projections and extending upwardly between saidprojections.

18. An elongated profiled tread for recapping tires having an outersurface of a predetermined curvature transverse to the circumference ofthe tire, said tread having a web portion having a bottom surfaceadapted to engage the outer surface of the tire to be recapped and aplurality of projections arranged spaced from each other in direction ofthe elongation of said tread and extending transverse to said directionand upwardly from said web portion, each of said projections beingformed with a cutout extending from said bottom surface into therespective projection and having in a plane extending in direction ofthe elongation of said tread normal to said bottom surface asubstantially triangular configuration, each of said cutouts taperingfrom a longitudinal edge of said tread toward a longitudinal plane ofsymmetry thereof.

19. An elongated profiled tread for recapping tires having an outersurface of a predetermined curvature transverse to the circumference ofthe tire, said tread having a web portion having a bottom surfaceadapted to engage the outer surface of the tire to be recapped and aplurality of projections arranged spaced from each other in direction ofthe elongation of said tread. and extending transverse to said directionand upwardly from said web portion, each of said projections beingformed. with a cutout extending from said bottom surface into therespective projection and having in a plane extending in direction ofthe elongation of said tread normal to said bottom surface asubstantially triangular configuration, each of said cutouts taperingfrom a longitudinal edge of said tread toward a longitudinal plane ofsymmetry there of; and at least one bore extending from the cutout ofeach projection to the exterior thereof.

29. An elongated profiled tread for recapping tires having an outersurface of a predetermined curvature transverse to the circumference ofthe tire, said tread having a web portion having a bottom surfaceadapted to engage the outer surface of the tire to be recapped and aplurality of projections arranged spaced from each other in direction ofthe elongation of said tread and. extending transverse to said directionand upwardly from said web portion, said tread being formed with aplurality of slits respectively extending from the bottom surface ofsaid tread into said projections.

21. An elongated profiled tread for recapping tires having an outersurface of a predetermined curvature transverse to the circumference ofthe tire, said tread having a web portion having a bottom surfaceadapted to engage the outer surface of the tire to be recapped and aplurality of projections arranged spaced from each other in direction ofthe elongation of said tread and extending transverse to said directionand upwardly from said. web portion, said tread being formed with aplurality of slits 1 1 1 2 respectively extending from the bottomsurface of said 2,421,099 5/ 1947 Vogt 156-96 I tread into saidprojections, and the flanks of each projec- 2,459,757 1/ 1949 Smith152-187 tion being provided with undercuts. 2,735,471 2/ 1956 McLean152187 References Cited by the Examiner 5 ARTHUR L. LA POINT, PrimaryExaminer. UNITED STATES PATENTS c. W. HAEFELE, Assistant Examiner.

2,392,590 1/1946 Hul-swit et a1. 15696

1. A TREAD SECTION FOR RECAPPING A TIRE OF A GIVEN RADISU, SAID TREAD SECTION HAVING AN INNER CONTINUOUSLY CURVED CONCAVE SURFACE ADAPTED TO ENGAGE THE OUTER SURFACE OF THE TIRE TO BE RECAPPED, SAID INNER CONCAVE SURFACE BEING CURVED IN THE DIRECTION OF THE CIRCUMFERENCE OF THE TIRE 